Redispersible, silicon-modified dispersion powder composition, process for its preparation and its use

ABSTRACT

The invention concerns a dispersion powder composition which is redispersible in water and is made from water-insoluble homopolymers or copolymers of preferably ethylenically unsaturated monomers and one or more organosilicon compounds plus, optionally, other additives such as protective colloids and anti-blocking agents. The composition is obtained by: a) polymerizing one or more monomers in the presence of 0.1 to 30% by wt., relative to the total weight of the monomers, of one or more silicon compounds which are dispersible in water and which have a boiling point at normal pressure of &gt;160° C., selected from the group comprising the silanes, polysilanes, oligosiloxanes, polysiloxanes, carbosilanes, polycarbosilanes, carbosiloxanes, polycarbosiloxanes and polysilylenedisiloxanes and: b) spray-drying the product thus obtained, either before or after addition of the additives mentioned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a silicon-modified dispersion powdercomposition which is redispersible in water and is based onwater-insoluble polymers, a process for its preparation and its use.

2. Background Art

Dispersion powder compositions which are redispersible in water and arebased on homo- or copolymers of ethylenically unsaturated monomers areknown. Such a dispersion powder composition is prepared by spray dryingthe corresponding aqueous plastics dispersions in a stream of hot air.The dispersion powders are suitable as additives to hydraulic binders inthe building materials industry, and such products are furthermoreemployed as binders in coating compositions or in adhesives.

EP-A 228657 (U.S. Pat. No. 4,704,416) describes dispersion powders whichare redispersible in water and are based on water-soluble polymers, andwhich comprise organic silicon compounds, preferablyorganopolysiloxanes. The dispersion powders are prepared by spray dryingan emulsion of the organic silicon compound in an aqueous solution ofthe water-soluble polymer.

EP-B 279373 relates to powders which are redispersible in water andcomprise organopolysiloxane, and which additionally comprise awater-soluble, film-forming polymer. They are prepared by spray dryingthe aqueous mixtures of the constituents mentioned,

EP-A 493168 relates to dispersion powders which are redispersible inwater and are based on film-forming, water-insoluble vinyl or acrylicpolymers, and which comprise silicones, more precisely organosiliconatesand/or organopolysiloxanes. They are prepared by spray drying aqueousdispersions of the vinyl or acrylic polymers, to which silicones havebeen added before the spraying. In this procedure, the silicones arepresent in emulsion and the water-insoluble polymers in dispersionbefore the spray drying, so that after the spray drying or theredispersion, products in which the components are present in separateparticles are obtained.

The invention was based on the object of providing dispersion powdercompositions which are redispersible in water and are based onwater-insoluble polymers, and which are modified with organosiliconcompounds in a manner such that the two components are present togetherin the powder particles and in the redispersed particles, and ifappropriate are bonded to one another via chemical bonds.

SUMMARY OF THE INVENTION

The invention relates to a dispersion powder composition which isredispersible in water and is based on water-insoluble homo- orcopolymers of preferably ethylenically unsaturated monomers and one ormore organosilicon compounds and, if appropriate, further additives,such as protective colloids and antiblocking agents, obtainable by

a) polymerization of one or more monomers in the presence of 0.1 to 30%by weight, based on the total weight of the monomers, of one or moreorganosilicon compounds which are dispersible in water and have aboiling point under normal pressure of >160° C., from the groupconsisting of silanes, polysilanes, oligosiloxanes, polysiloxanes,carbosilanes, polycarbosilanes, carbosiloxanes, polycarbosiloxanes andpolysilylenedisiloxanes and

b) spray drying of the product thus obtained, if appropriate before orafter addition of the additives mentioned.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred water-insoluble polymers are:

vinyl ester homo- or copolymers containing one or more monomer unitsfrom the group consisting of vinyl esters of unbranched or branchedalkylcarboxylic acids having 1 to 15 C atoms;

(meth)acrylic acid ester homo- or copolymers containing one or moremonomer units from the group consisting of methacrylic acid esters andacrylic acid esters of unbranched or branched alcohols having 1 to 12 Catoms;

homo- or copolymers of fumaric and/or maleic acid mono- or diesters ofunbranched or branched alcohols having 1 to 12 C atoms;

homo- or copolymers of dienes, such as butadiene or isoprene, and ofolefins, such as ethene or propene, it being possible for the dienes tobe copolymerized, for example with styrene, (methacrylic acid esters orthe esters of fumaric of maleic acid;

homo- or copolymers of vinyl aromatics, such as styrene, methylstyreneor vinyltoluene;

homo- or copolymers of vinyl halogen compounds, such as vinyl chloride.

Where appropriate, water-insoluble, film-forming polyaddition andpolycondensation polymers, such as polyurethanes polyesters, polyethers,polyamides, epoxy resins, melamine-formaldehyde resins orphenol-formaldehyde resins, which are accessible by polymerization ofthe corresponding monomers or oligomeric compounds, are also suitable.

Preferred vinyl esters are vinyl acetate, vinyl propionate, vinylbutyrate, vinyl 2-ethylhexanoate, vinyl laurate, 1-methylvinyl acetate,vinyl pivalate and vinyl esters of α-branched monocarboxylic acidshaving up to 10 C atoms, for example VeoVa9^(R) or VeoVa10^(R). Vinylacetate is particularly preferred.

Preferred methacrylic acid esters or acrylic acid esters are methylacrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate,propyl acrylate, propyl methacrylate, n-butyl acrylate, t-butylacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexylacrylate. Methyl acrylate, methyl methacrylate, n-butyl acrylate and2-ethylhexyl acrylate are particularly preferred.

Preferred ester groups of fumaric and maleic acid are the methyl, ethyl,n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, hexyl, ethylhexyl anddodecyl group.

If appropriate, the vinyl ester copolymers can comprise 1.0 to 65% byweight, based on the total weight of the comonomer phase, of α-olefins,such as ethylene or propylene, and/or vinyl aromatics, such as styrene,and/or vinyl halides, such as vinyl chloride, and/or acrylic acid eatersor methacrylic acid esters of alcohols having 1 to 10 C atoms, such asmethyl acrylate, methyl methacrylate, ethyl acrylate, ethylmethacrylate, propyl acrylate, propyl methacrylate, n-butyl acrylate,t-butyl acrylate, n-butyl methacrylate, t-butyl methacrylate and2-ethylhexyl acrylate and/or ethylenically unsaturated dicarboxylic acidesters or derivatives thereof, such as diisopropyl fumarate, thedimethyl, methyl t-butyl, di-n-butyl, di-t-butyl and diethyl esters ofmaleic acid or fumaric acid, or maleic anhydride.

If appropriate, the (meth)acrylic acid ester copolymers can comprise 1.0to 65% by weight, based on the total weight of the comonomer phase, ofα-olefins, such as ethylene or propylene, and/or vinyl aromatics, suchas styrene, and/or vinyl halides, such as vinyl chloride, and/orethylenically unsaturated dicarboxylic acid esters or derivativesthereof, such as diisopropyl fumarate, the dimethyl, methyl butyl,dibutyl and diethyl esters of maleic acid or fumaric acid, or maleicanhydride,

In a preferred embodiment, the vinyl ester copolymers and the(meth)acrylic acid ester copolymers also comprise 0.05 to 10.0% byweight, based on the total weight of the comonomer mixture, of auxiliarymonomers from the group consisting of ethylenically unsaturatedcarboxylic acids, preferably acrylic acid or methacrylic acid; from thegroup consisting of ethylenically unsaturated carboxylic acid amides,preferably acrylamide; from the group consisting of ethylenicallyunsaturated sulphonic acids and salts thereof, preferably vinylsulphonicacids; and/or from the group consisting of polyethylenically unsaturatedcomonomers, for example divinyl adipate, diallyl maleate, allylmethacrylate or triallyl cyanurate. Suitable auxiliary monomers are alsocomonomers having a crosslinking action, for example acrylamidoglycolicacid (AGA), methylacrylamidoglycolic acid methyl ester (MAGME),N-methylolacrylamide (NMAA), N-methylolmethacrylamide, allylN-methylolcarbamate and alkyl ethers, such as the isobutoxy ether, oresters of N-methylolacrylamide, of N-methylolmethacrylamide or

Corresponding statements to those for the (meth)acrylic acid estercopolymers apply to the copolymers of esters of maleic or fumaric acid.

In the most preferred embodiment, the ethylenically unsaturated monomersare copolymerized with 0.02 to 5.0% by weight, preferably 0.05 to 2.0%by weight, based on the total weight of the monomers, of ethylenicallyunsaturated silicon compounds which contain at least one hydrolysablegroup bonded to a silicon atom or at least one Si--OH group, Suitableethylenically unsaturated silicon compounds can be summarized by thegeneral formula R¹ --SiR_(a) (OR²)_(3-a), where a=0 to 2, wherein R isidentical or different and denotes branched or unbranched alkyl radicalshaving 1 to 22 C atoms, cycloalkyl radicals having 3 to 10 C atoms,alkylene radicals having 2 to 4 C atoms or aryl, aralkyl or alkylarylradicals having 6 to 18 C atoms, where the radicals R mentioned can alsobe substituted by halogens, such as F or Cl, by ether, thioether, ester,amide, nitrile, hydroxyl, amine, epoxide, carboxyl, carboxylic acidanhydride and carbonyl groups, R¹ is an ethylenically unsaturatedorganic radical and R² denotes identical or different radicals from thegroup consisting of hydrogen, C₁ -C₆ -alkyl or alkoxyalkylene radical.The boiling point of these compounds is insignificant. If appropriate,these compounds can also be water-soluble.

Preferred silicon-containing monomers are compounds of the generalformulae;.

    CH.sub.2 ═CH--(CH.sub.2).sub.0-8 --SiR.sup.3.sub.a (OR.sup.4).sub.3-a,

    CH.sub.2 ═CR.sup.5 --CO.sub.2 --(CH.sub.2).sub.b --SiR.sup.3.sub.a (OR.sup.4).sub.3-a, ##STR1##

    HS(CH.sub.2).sub.b --SiR.sup.3.sub.a (OR.sup.4).sub.3-a, ##STR2## where

a=0-2,

b=1-6, R³ =CH₃, C₆ H₅, R⁴ ═H, CH₃, C₂ H₅, C₃ H₇, C₆ H₅, (CH₂)₂₋₃--O--(CH₂)₁₋₂ H and R₅ ═H, CH₃.

Particularly preferred silicon-containing mono

    HS(CH.sub.2).sub.b --SiR.sup.3.sub.a (OR.sup.4).sub.3-1, ##STR3## where

a=0-2,

b=1-6, R³ ═CH₃, C₆ H₅, R⁴ ═H, CH₃, C₂ H₅, C₃ H₇, C₆ H₅, (CH₂)₂₋₃--O--(CH₂)₁₋₂ H and R⁵ ═H, CH₃.

Particularly preferred silicon-containing monomers are γ-acryl- orγ-methacryloxypropyltri(alkoxy)-silanes and vinyltrialkoxysilanes,alkoxy groups which can be employed being, for example, methoxy, ethoxy,methoxyethylene, ethoxyethylene, methoxypropylene glycol ether orethoxypropylene glycol ether radicals. Vinyltrimethoxy- andvinyltriethoxysilane and γ-methacryloxypropyltriethoxysilane are mostpreferred.

Preferred non-copolymerizable organosilicon compounds which aredispersible in water and have a boiling point >160° C. (under normalpressure) from the group consisting of silanes, polysilanes,oligosiloxanes, polysiloxanes, carbosilanes, polycarbosilanes,carbosiloxanes, polycarbosiloxanes and polysilylenedisiloxanes are:

silicic acid esters Si(OR')₄, organoorganoxysilanes SiR_(n) (OR')_(4-n),where n=1 to 3, organosilanols SiR_(n) (OH)_(4-n), where n=1 to 3,polysilanes of the general formula R₃ Si(SiR₂)_(n) SiR₃ where n=0 to500, preferably 0 to 8, and di-, oligo- and polysiloxanes of units ofthe general formula R_(c) H_(d) Si(OR')_(e) (OH)_(f) O.sub.(4-c-d-e-f)/2where c=0 to 3, d=0 to 1, e=0 to 3,f=0 to 3 and the sum c+d+e+f per unitis not more than 3.5, wherein R' represents identical or different alkylradicals or alkoxyalkylene radicals having 1 to 4 C atoms, preferablydenotes methyl or ethyl, and R is identical or different and denotesbranched or unbranched alkyl radicals having 1 to 22 C atoms, cycloalkylradicals having 3 to 10 C atoms, alkylene radicals having 2 to 4 Catoms, aryl, aralkyl or alkylaryl radicals having 6 to 18 C atoms, wherethe radicals R mentioned can also be substituted by halogens, such as For Cl, by ether, thioether, ester, amide, nitrile, hydroxyl, amine,carboxyl, sulphonic acid, carboxylic acid anhydride and carbonyl groups,where, in triethoxysilane, dipropyldiethoxysilane,methylphenyldiethoxysilane, diphenyldimethoxysilane, triphenylsilanoland preferably liquid condensation products thereof, if appropriate withother low-boiling and/or water-soluble silanes, such asmethyltrimethoxysilane, γ-aminopropyltriethoxysilane or other silanescontaining amino functions, such as

    H.sub.2 NCH.sub.2 CH.sub.2 NHCH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3, ##STR4## silanes containing quaternary ammonium salt groups, such as C.sub.18 H.sub.37 N.sup.⊕ (CH.sub.3).sub.2 --CH.sub.2 CH.sub.2 CH.sub.2 Si(OCH.sub.3).sub.3 Cl.sup.⊖, silanes containing epoxide groups, such as ##STR5## and silanes containing carboxylic acid and carboxylic acid anhydride functional groups, such as ##STR6##

Compounds which may furthermore be mentioned are: the disilanesdimethyltetraalkoxydisilane, tetramethyldialkoxydisilane andtrimethyltrialkoxydisilane, or (co)condensates thereof which are ingeneral obtainable from the corresponding chlorine compounds.Methylhydridopolysiloxanes terminally blocked by trimethylsiloxy groups,copolymers, terminally blocked by trimethylsiloxy groups, ofdimethylsiloxane and methylhydridosiloxane units, anddimethylpolysiloxanes containing in each case one Si-bonded hydroxylgroup in the terminal units are also particularly preferred. There mayalso be mentioned organosilicon compounds, which are soluble in themonomers, from the group consisting of alkyl and phenyl resins and theresins and oils which contain epoxide or amine, propyl or higher alkylgroups.

Preparation of the organosilicon compounds can be carried out byprocesses such as are described in Noll, Chemie und Technologie derSilicone Chemistry and technology of the silicones!, 2nd edition 1968,Weinheim and in Houben-Weyl, Methoden der organischen Chemie Methods oforganic chemistry!, Volume E20, page 1782 et seq., 2219 et seq., GeorgThieme Verlag, Stuttgart, 1987.

The polymerization is preferably carried out by the emulsionpolymerization process, but can also be carried out by means of theblock or the solution polymerization process. Water-sensitive monomers,such as amine, propyl or higher alkyl groups.

Preparation of the organosilicon compounds can be carried out byprocesses such as are described in Noll, Chemie und Technologie derSilicone Chemistry and technology of the silicones!, 2nd edition 1968,Weinheim and in Houben-Weyle Methoden der organischen Chemie Methods oforganic chemistry!, Volume E20, page 1782 et seq., 2219 et seq., GeorgThieme Verlag, Stuttgart,, 1987.

The polymerization is preferably carried out by the emulsionpolymerization process, but can also be carried out by means of theblock or the solution polymerization process. Water-sensitive monomers,such as ketene acetals, which can be polymerized by free radicals canalso be polymerized by the last two processes mentioned. Addition andpolycondensation polymers are furthermore accessible by these processes.In these cases, the compositions of polymer and organosilicon,compound(s) dissolved in organic, water-insoluble solvents areemulsified with the aid of the water-soluble, film-forming protectivecolloids, mentioned below, and if appropriate emulsifiers, and theemulsions are spray dried, if appropriate after addition of furtheradditives.

The emulsion polymerization process, which is mentioned as preferred, iscarried out in an open reaction vessel or in pressure vessels,preferably in a temperature range from 0° to 100° C., and is initiatedby the methods usually employed for emulsion polymerization. Theinitiation is carried out by means of the customary, at least partlywater-soluble agents which form free radicals, which are preferablyemployed in amounts of 0.01 to 3.0% by weight, based on the total weightof the monomers. Examples of these agents are ammonium and potassiumpersulphate and peroxodisulphate; hydrogen peroxide and t-butylperoxide; alkyl hydroperoxides, such as tert-butyl hydroperoxide;potassium, sodium and ammonium peroxodiphosphate; and azo compounds,such as azobisisobutyronitrile or azobiscyanovaleric acid. Ifappropriate, the free radical initiators mentioned can also be combinedin a known manner with 0.01 to 1.0% by weight, based on the total weightof the monomers, of reducing agents. Suitable reducing agents are, forexample, alkali metal formaldehyde-sulphoxylates and ascorbic acid. Inthe case of redox initiation, one or both redox catalyst components arepreferably metered in here during the polymerization.

Dispersing agents which can be employed are all the emulsifiers and/orprotective colloids usually used in emulsion polymerization. Bothanionic and cationic as well as nonionic emulsifiers are suitableemulsifiers. Those which are not soluble in the protective colloid andhave molecular weights, in contrast to the protective colloid, of below2000 are preferred. The emulsifiers are is employed in an amount of 0 to6% by weight, based on the total weight of the monomers, Suitableemulsifiers are familiar to the expert and are to be found, for example,in Houben-Weyl, Methoden der organischen Chemie Methods of organicchemistry!, Volume XIV, 1, Makromalekulare Stoffe Macromolecularsubstances!, Georg Thieme Verlag, Stuttgart, 1961, 192-208.

The protective colloids are preferably employed in amounts of up to 15%by weight, based on the total weight of the monomers. Examples of theseare vinyl alcohol/vinyl acetate copolymers having a content of 80 to 100mol % of vinyl alcohol units; polyvinylpyrrolidones having a molecularweight of 5000 to 400,000; hydroxyethylcelluloses having a degree ofsubstitution range from 1.5 to 3; polysaccharides in water-soluble form,such as starches (amylose and amylopectin), cellulose, guar,tragacanthic acid, dextran, alginates and carboxymethyl, methyl,hydroxyethyl and hydroxypropyl derivatives thereof; proteins, such ascasein, soya protein and gelatine a synthetic polymers, such aspoly(meth)acrylic acid, poly(meth)acrylamide, polyvinylsulphonic acidsand water-soluble copolymers thereof; andmelamine-formaldehydesulphonates, naphthalene-formaldehydesulphonates,and styrene/maleic acid and vinyl ether/maleic acid copolymers, In aparticularly preferred embodiment, the polymerization is carried outwith a protective colloid without addition of an emulsifier.

The pH range desired for the polymerization, which is in general between2.5 and 10, preferably 3 and 8, can be established in a known manner byacids, bases or customary buffer salts, such as alkali metal phosphatesor alkali metal carbonates. To establish the molecular weight, theregulators usually used, for example mercaptans, aldehydes andchlorinated hydrocarbons, can be added during the polymerization.

Regardless of the polymerization process chosen, the polymerization canbe carried out discontinuously or continuously, with or without the useof seed latices, with initial introduction of all the constituents orindividual constituents of the reaction mixture, or with initialintroduction of a portion of the constituents or of individualconstituents of the reaction mixture and subsequent metering of theconstituents or individual constituents of the reaction mixture, or bythe metering method without an initial charge.

The organosilicon compound, which is dispersible in water, is preferablymetered in, individually or as a mixture, only in the course of thepolymerization. Metering is particularly preferably carried out after aconversion of 50 to 98%, most preferably 80 to 95%. The metering can becarried out in solution in one or more organic monomers, or separatelyin the pure form, or as an emulsion. Preferably, 0.5 to 20%, based onthe total weight of the monomer phase, of organosilicon compounds isadded.

In the most preferred embodiment, the ethylenically unsaturatedsilicon-containing monomers already mentioned are additionallycopolymerized with the organic monomers. These monomers, in the pureform, in solution, for example in the organic monomers, or as anemulsion, if appropriate with the organic monomers, can be initiallyintroduced or metered in during the polymerization. They are preferablyadded after more than 50%, particularly preferably more than 80%, of theethylenically unsaturated organic copolymers are polymerized.

The solids content of the dispersions thus obtainable is 20 to 60%.

In the case of preparation of silicon-modified redispersible powders ofpolyurethanes, polyesters, polyamides, melamine-formaldehyde resins andphenolformaldehyde and epoxy resins, these products are prepared by thepolymerization processes customary therefor in the presence of theorganosilicon compound(s), preferably in an organic solvent. In apreferred embodiment, organosilicon compounds which contain functionalgroups, such as the epoxide, amino or carbonyl group, which can reactwith the organopolymers are employed here. The compositions, dissolvedin organic water-insoluble solvents, of polymer and organosiliconcompound(s) are emulsified with the water-soluble film-formingprotective colloids mentioned below and, if appropriate, withemulsifiers before the spray drying.

By the procedure according to the invention, copolymerization ofSi-containing monomers gives a dispersion of particles in which theorganopolymer is at least partly bonded to the organosilicon compoundvia C--Si--O--Si bonds, in the form of graft copolymers. Ifpolymerization is carried out without Si-containing monomers, theorganosilicon compound and the organopolymer are often in the form ofinterpenetrated networks (IPN) or semiinterpenetrated networks or as amixture in the same dispersion particles. The wide range of variation ofthe internal structure of the redispersion powder particles which isthus possible allows optimization for the particular field of usewithout great technical expenditure by means of minor changes to thepreparation process and the recipe.

Drying of the dispersion for preparation of the dispersion powdercomposition is carried out by means of spray drying in customary spraydrying units, it being possible for the atomization to be effected bymeans of single-, dual- or multicomponent nozzles or with a rotatingdisc, The discharge temperature is in general chosen in the range from55° C. to 100° C., preferably 70° to 90° C., depending on the unit, theTg of the resin and the desired degree of drying.

If appropriate, a mixture of the dispersion prepared according to theinvention having a solids content of preferably 20 to 60% and of otheradditives can be sprayed and dried together during the spray drying.

In a preferred embodiment, the dispersion powder composition comprises 8to 50% by weight, preferably 10 to 25% by weight, of protective colloid,based on the total amount of water-insoluble polymer and organosiliconcompound, at least some of the amount of protective colloid in thefinished dispersion or the solution of the composition of polymer andorganosilicon compound being added before the spray drying, preferablyin the form of an aqueous solution. Suitable protective colloids are,for example, polyvinyl alcohols and derivatives thereof; polysaccharidesin water-soluble form, such as starches (amylose and amylopectin),cellulose, guar, tragacanthic acid, dextran, alginates andcarboxymethyl, methyl, hydroxyethyl and hydroxypropyl derivativesthereof; proteins, such as casein, soya protein and gelatine; syntheticpolymers, such as poly(meth)acrylic acid, poly(meth)acrylamide,polyvinylsulphonic acids and water-soluble copolymers thereof; andmelamine-formaldehydesulphonates, naphthalene-formaldehydesulphonates,and styrene/maleic acid and vinyl ether/maleic acid copolymers.

Where appropriate, other constituents of the dispersion powdercomposition are emulsifiers which are not soluble in the protectivecolloids employed, and antiblocking agents, such as Ca carbonate or Mgcarbonate, talc, gypsum, silicic acid and silicates having particlesizes preferably in the range from 10 nm to 10 μm.

The dispersion powder composition can be employed in the typical fieldsof use. For example, in chemical building products in combination Withinorganic, hydraulically setting binders, such as cements (Portland,aluminate, trass, Hullen, magnesia or phosphate cement), gypsum orwater-glass, for the preparation of building adhesives, plasters,stopper compositions, flooring stopper compositions, joint mortars andpaints, Furthermore as sole binders for coating compositions andadhesives or as binders for textiles,

The dispersion powder composition is preferably employed as ahydrophobizing binder in fields of use where, in addition to goodadhesion, a reduced uptake of water and/or a water-repellent effect isalso desired. As can also be seen from the results of the use test, avery low water uptake results when the dispersion powder compositionaccording to the invention is used, for example, in plasters, withoutthe other mechanical properties being influenced in an adverse manner,

EXAMPLES

Preparation of the dispersion powder compositions:

Example 1:

A solution of 6400 g of vinyl acetate, 320 g of isooctyltriethoxysilaneand 7 g of methaeryloxypropyltriethoxysilane was emulsified into asolution of 524 g of a polyvinyl alcohol having a Hoppler viscosity of 4mpas (in a 4% strength solution at 20° C.) and a hydrolysis number of140 in 4890 g of water in an 18 l autoclave. 1480 g of ethylene wereforced in and polymerization was carried out at 50° C. with the redoxcatalyst system of 26 g of potassium persulphate (3% strength aqueoussolution) and 13 g of Bruggolit (Na formaldehyde-sulphoxylate; 1.5%strength aqueous solution in the course of 4 hours. A dispersion havinga solids content of 57% resulted.

After the autoclave had been let down, 5 parts, calculated on 100 partsof dispersion, of a polyvinyl alcohol having a Hoppler viscosity of 25mPas (in a 4% strength solution at 20° C.) and a hydrolysis number of140 were stirred into the dispersion and the solids content of thedispersion was then adjusted to 33% with water. The dispersion wassprayed in a Nebulosa spray drier under the following conditions;

intake temperature: about 112° C.,

discharge temperature; 80° C.,

compressed air pressure upstream of 2-component nozzle: 4 bar,

throughput: 12 l/hour.

After the spraying, 10% by weight, based on the spray-dried product, ofa commercially available antiblocking agent (mixture of Ca/MgCO₃ and Mghydrosilicate) was incorporated, The dry powder was very readilyfree-flowing and redispersible in water.

Example 2:

The procedure was analogous to Example 1, with the difference thatvinyltriethoxysilane was copolymerized instead ofmethacryloxypropyltriethoxysilane. The dry powder thus obtained was veryreadily free-flowing and redispersible in water.

Example 3:

Example 1 was repeated but instead of isooctyltriethoxysilane, 4% byweight, based on the amount of comonomer, of an isooctyltrimethoxysilaneinitially condensed with 1.5 mol of water per 2 mol of silane was used.The powder thus obtained was very readily free-flowing and redispersiblein water.

Example 4:

Example 2 was repeated, but the copolymerizable and thenon-copolymerizable silane were not dissolved in the initial mixture invinyl acetate, but added to the initial mixture in a mixture as anemulsion. The powder thus obtained was very readily free-flowing andredispersible in water.

Example 5:

Example 2 was modified to the extent that the silane mixture wasdissolved in 10% of the vinyl acetate and this solution was metered inonly as the polymerization started to subside (90% conversion). Thepowder thus obtained was very readily free-flowing and redispersible inwater.

Example 6:

The procedure was analogous to Example 3, with the difference that nomethacryloxypropyltriethoxysilane was copolymerized. The powder thusobtained was very readily free-flowing and redispersible in water,

Example 7:

A mixture of 568 g of n-butyl acrylate in 568 g of styrene wasemulsified into a solution of 320 g of polyvinyl alcohol (Hopplerviscosity 4 mPas in a 4% strength solution at 20° C., hydrolysisnumber=140) and 290 g of a polyvinyl alcohol containing carbonyl groups(LL 620, product of Wacker-Chemie) in 7140 g of water in an 18 l reactorand the emulsion was heated to 80° C. While keeping the temperatureconstant, the polymerization was initiated by addition of t-butylperoxide (5% strength aqueous solution) and Na formaldehydesulphoxylate(8% strength aqueous solution). The total consumption was, overall, 44 gof t-butyl hydroperoxide and 70 g of Na formaldehyde-sulphoxylate. 5minutes after the internal temperature started to rise, a mixture of3220 g of n-butyl acrylate and 3220 g of styrene was metered in over aperiod of 4 hours. After 3.5 hours had passed, 325 g ofisooctyltriethoxysilane and 7 g of methacryloxypropyltriethoxysilanewere metered in with the remaining n-butyl acrylate/styrene mixture.After the end of the metering, polymerization was carried out at 80° C.for one hour and after-polymerization was finally carried out at 45° C.for 3 hours. In each case 2.5% by weight, based on the total weight ofthe dispersion, of a polyvinyl alcohol having a Hoppler viscosity of 25mPas in 4% strength aqueous solution at 20° C. and a hydrolysis numberof 140 and of a polyvinyl alcohol having a Hoppler viscosity of 13 mPasin 4% strength aqueous solution at 20° C. and a hydrolysis number of 140were added to the dispersion thus obtained and the dispersion wasdiluted with water to a solids content of 33%. Spraying was carried outanalogously to Example 1. The powder thus obtained was very readilyredispersible and free-flowing.

Example 8:

The procedure was analogous to Example 7, with the difference thatinstead of methacryloxypropyltriethoxysilane, the same amount ofvinyltriethoxysilane was used and was metered in together with theisooctyltriethoxysilane from the start, with the n-butylacrylate/styrene mixture. The powder thus obtained was very readilyfree-flowing and redispersible in water.

Comparison Example 1:

The procedure was analogous to Example 1, but the polymerization wascarried out without the addition of isooctyltriethoxysilane and withoutcopolymerization of methacryloxypropyltriethoxysilane. A powder whichwas very readily free-flowing and redispersible in water was obtained.

Comparison Example 2:

The procedure was analogous to Example 7, but the polymerization wascarried out without the addition of isooctyltriethoxysilane and withoutcopolymerization of methacryloxypropyltriethoxysilane. A powder whichwas very readily free-flowing and redispersible in water was obtained.

Use test:

The products prepared in the Examples and the Comparison Examples wereemployed in the following rolling plaster or joint filler recipe:

Rolling plaster recipe:

452.0 parts of Inducarb 500 (CaCO₃, 0.03-0.5 mm)

200.0 parts of Inducarb 0000 (CaCO₃, 0.4-0.9 mm)

150.0 parts of white cement PZ 45 F

80.0 parts of hydrated lime 2741

40.0 parts of Kronos 2056 (TiO₂ pigment)

15.0 parts of Arbocel BC 1000 (cellulose fibre)

2.0 parts of Culminal MC 3000 PR (cellulose ether)

1.0 part of Amylotex 8100 (starch ether)

60.0 parts of dispersion powder composition water requirement per 1000 gof dry mixture: about 350 ml

Joint filler recipe:

300.0 parts of Portland cement PZ 35 F

40.0 parts of aluminate cement

649.5 parts of quartz sand (0.1-0.4 mm)

0.5 part of Culminal C 8556 (cellulose ether)

10.0 parts of dispersion powder composition water requirement per 1000 gof dry mixture: 200 ml

Testing the joint filler recipe:

The compressive strength of plasters prepared with these recipes wastested in accordance with DIN 1164. The water uptake was determined inaccordance with DIN 52617 after storage of the recipe in the dry statefor 14 days at 23° C./50% relative atmospheric humidity. Theprocessability was evaluated qualitatively. The results of the testingare summarized in Table 1.

Testing the rolling plaster recipe:

The adhesive tensile strength of plasters prepared with these recipeswas tested in accordance with DIN 1164. Using method A, the measurementwas made after storage in the dry state for 28 days at 23° C./50%relative atmospheric humidity. Using method B, the measurement was madeafter storage in the dry state for 7 days at 23° C./50% relativeatmospheric humidity and storage under water for a further 21 days at23° C. The flexural tensile strength and compressive strength weredetermined in accordance with the abovementioned standard after storagein the dry state for 28 days at 23° C./50% relative atmospherichumidity.

The water uptake coefficient was determined in accordance with DIN 52617after storage of the recipe in the dry state for 14 days at 23° C./50%relative atmospheric humidity.

The results of testing are summarized in Table 2.

                  TABLE 1                                                         ______________________________________                                        (Testing of the joint filler receipe)                                         Example       Example 6   Comparison Example 1                                ______________________________________                                        Water uptake  0.197 ± 0.005                                                                          0.759 ± 0.020                                    (kg/m.sup.2 × h.sup.0.5)                                                Compressive strength                                                                        16.0 ± 0.3                                                                             17.4 ± 0.5                                       (N/mm.sup.2)                                                                  Processability                                                                              somewhat tacky                                                                            somewhat tacky                                      ______________________________________                                    

                                      TABLE 2                                     __________________________________________________________________________    (Testing of the rolling plaster recipe)                                       Example  Example 1                                                                            Example 2                                                                            Example 3                                                                            Example 4                                                                            Example 5                                                                            Comp. Ex. 1                       __________________________________________________________________________    Adhesive strength                                                             Method A (N/mm.sup.2)                                                                  0.783 ± 0.049                                                                     0.755 ± 0.113                                                                     0.806 ± 0.014                                                                     0.795 ± 0.093                                                                     1.020 ± 0.080                                                                     0.679 ± 0.33                   Method B (N/mm.sup.2)                                                                  0.765 ± 0.072                                                                     0.778 ± 0.053                                                                     0.640 ± 0.036                                                                     0.803 ± 9.120                                                                     0.926 ± 0.032                                                                     0.694 ± 0.029                  Flexural tensile                                                                       2.61 ± 0.03                                                                       2.21 ± 0.06                                                                       2.39 ± 0.06                                                                       2.31 ± 0.10                                                                       2.80 ± 0.14                                                                       2.22 ± 0.06                    strength (N/mm.sup.2)                                                         Compressive                                                                            3.08 ± 0.18                                                                       2.55 ± 0.14                                                                       3.03 ± 0.17                                                                       2.53 ± 0.21                                                                       3.58 ± 0.04                                                                       2.54 ± 0.11                    strength (N/mm.sup.2)                                                         Water uptake                                                                           0.164 ± 0.043                                                                     0.071 ± 0.019                                                                     0.077 ± 0.016                                                                     0.079 ± 0.017                                                                     0.082 ± 0.011                                                                     0.351 ± 0.065                  (kg/m.sup.2 × h.sup.0.5)                                                __________________________________________________________________________

We claim:
 1. A dispersible powder composition which is redispersible inwater and is comprising water-insoluble polymers of ethylenicallyunsaturated monomers and, one or more organosilicon compounds and,optionally additives, said composition being prepared bya)polymerization of one or more monomers in the presence of 0.1 to 30% byweight, based on the total weight of the monomers, of one or morenon-copolymerizable organosilicon compounds which are dispersible inwater and have a boiling point under normal pressure of >160° C.,selected from the group consisting of silanes, polysilanes,oligosiloxanes, polysiloxanes, carbosilanes, polycarbosilanes,carbosiloxanes, polycarbosiloxanes and polysilylenedisiloxanes and b)spray drying the emulsion thus obtained, before or after addition of anyadditives.
 2. The dispersible powder composition according to claim 1,which is obtainable by emulsion polymerization of one or more monomersselected from the group consisting of vinyl esters of unbranched orbranched alkylcarboxylic acids having 1 to 15 C atoms; of methacrylicacid esters and acrylic acid esters of unbranched or branched alcoholshaving 1 to 12 C atoms; of fumaric and/or maleic acid mono- or diestersof unbranched or branched alcohols having 1 to 12 C atoms; of dienes,and of olefins, it being possible for the dienes to be copolymerized, ofvinyl aromatics, and of vinyl halogen compounds.
 3. Dispersible powdercomposition according to claim 1 which is obtainable by copolymerizationof the ethylenically unsaturated monomers with 0.02 to 5.0% by weight,based on the total weight of the monomers, of ethylenically unsaturatedsilicon compounds with the general formula R¹ --SiR_(a) (OR²)_(3-a),where a=0 to 2, wherein R is identical or different and denotes branchedor unbranched alkyl radicals having 1 to 22 C atoms, cycloalkyl radicalshaving 3 to 10 C atoms, or aryl, aralkyl or alkylaryl radicals having 6to 18 C atoms, where the radicals R mentioned can also be substituted byhalogens, such as F or Cl, by ether, thioether, ester, amide, nitrile,hydroxyl, amine, epoxide, carboxyl, carboxylic acid anhydride andcarbonyl groups, R¹ is an ethylenically unsaturated organic radical andR² denotes identical or different radicals from the group consisting ofhydrogen, C₁ -C₆ -alkyl or alkoxyalkylene radical.
 4. Dispersible powdercomposition according to claim 3, wherein one or more compounds of thegeneral formulae

    CH.sub.2 ═CH--(CH.sub.2).sub.0-8 --SiR.sup.3.sub.a (OR.sup.4).sub.3-a,

    CH.sub.2 ═CR.sup.5 --CO.sub.2 --(CH.sub.2).sub.b --SiR.sup.3.sub.a (OR.sup.4).sub.3-a, ##STR7## where a=0-2, b=1-6, R.sup.3 ═CH.sub.3, C.sub.6 H.sub.5, R.sup.4 ═H, CH.sub.3, C.sub.2 H.sub.5, C.sub.3 H.sub.7, C.sub.6 H.sub.5, (CH.sub.2)2-3--O--(CH.sub.2).sub.1-2 H and R.sup.5 ═H, CH.sub.3, are copolymerized as the ethylenically unsaturated silicon compounds.


5. Dispersible powder composition according to claim 1, wherein theemulsion polymerization is carried out in the presence of one of moreorgano-silicon compounds which are dispersible in water, and have aboiling point >160° C. under normal pressure and are selected from thegroup consisting of silicic acid esters Si(OR')₄, organoorganoxysilanesSiR_(n) (OR')_(4-n), where n=1 to 3, organosilanols SiR_(n) (OH)_(4-n),where n=1 to 3, polysilanes of the general formula R₃ Si(SiR₂)_(n) SiR₃where n=0 to 500, and di-, oligo- and polysiloxanes of units of thegeneral formula R_(c) H_(d) Si(OR')_(e) (OH)_(f) O_(4-c-d-e-f))/2 wherec=0 to 3, d=0 to 1, e=0 to 3,f=0 to 3 and the sum c+d+e+f per unit isnot more than 3.5, wherein R' represents identical or different alkylradicals or alkoxyalkylene radicals having 1 to 4 C atoms, and R isidentical or different and denotes branched or unbranched alkyl radicalshaving 1 to 22 C atoms, cycloalkyl radicals having 3 to 10 C atoms,aryl, aralkyl or alkylaryl radicals having 6 to 18 C atoms, where theradicals R mentioned can also be substituted by halogens, such as F orCl, by ether, thioether, ester, amide, nitrile, hydroxyl, amine,carboxyl, sulphonic acid, carboxylic acid anhydride and carbonyl groups,where, in the case of the polysilanes, R can also have the meaning OR'.6. Process for the preparation of dispersible powder compositionsaccording to claim 1 by means ofa) emulsion polymerization in an openreaction vessel or in pressure vessels, in a temperature range from 0°to 100° C., initiated with the at least partly water-soluble agentswhich form free radicals and which are usually employed for emulsionpolymerization, emulsifiers and/or protective colloids being employed asdispersing agents, and the polymerization being carried outdiscontinuously or continuously, with or without the use of seedlatices, with initial introduction of all the constituents or individualconstituents of the reaction mixture, or with initial introduction of aportion of the constituents or of individual constituents of thereaction mixture and subsequent metering of the constituents orindividual constituents of the reaction mixture, or by the meteringmethod without an initial charge and b) optionally adding a protectivecolloid before or after the spray drying.
 7. Process according to claim6, wherein the non-copolymerizable organosilicon compound which isdispersible in water, individually or as a mixture, is initiallyintroduced or is metered in only in the course of the polymerization,the metering being carried out in solution in one or more organicmonomers, or separately in the pure form, or as an emulsion.
 8. Processaccording to claim 6 wherein the ethylenically unsaturatedsilicon-containing monomers are initially introduced or are metered inonly in the course of the polymerization, the metering being carried outin solution, in the pure form or as an emulsion.
 9. The dispersiblepowder composition of claim 1 wherein the additives are protectivecolloids or antiblocking agents.
 10. The dispersible powder compositionof claim 2 wherein the dienes are butadiene or isoprene; the olefins areethene or propane, the dienes can be copolymerized with styrene,(meth)acrylic acid esters or the esters of fumaric or maleic acid; thevinyl aromatics are styrene, methylstyrene or vinyltoluene, and thevinyl halogen compound is vinyl chloride.
 11. The dispersible powdercomposition of claim 5 wherein R' represents methyl or ethyl.